Positioning device, electronic instrument, and filter passband changing method

An RF receiver circuit section extracts a signal including the frequency band of a GPS satellite signal by causing a signal received from a GPS satellite to pass through a filter section that includes a plurality of filters having different passbands, and outputs the extracted signal to a baseband process circuit section. The baseband process circuit section exclusively switches the filter of the filter section based on the signal strength of the signal output from the RF receiver circuit section, and the present position of a portable telephone is located based on the signal output from the RF receiver circuit section.